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Bài 2: 1) Ta có: \[ \frac{2}{3} - 4 \left( \frac{1}{2} + \frac{3}{4} \right) \] \[ = \frac{2}{3} - 4 \left( \frac{2}{4} + \frac{3}{4} \right) \] \[ = \frac{2}{3} - 4 \left( \frac{5}{4} \right) \] \[ = \frac{2}{3} - 5 \] \[ = \frac{2}{3} - \frac{15}{3} \] \[ = \frac{2 - 15}{3} \] \[ = \frac{-13}{3} \] 2) Ta có: \[ \frac{1}{7} + \frac{6}{7} \left( \frac{1}{2} - \frac{1}{3} \right) \] \[ = \frac{1}{7} + \frac{6}{7} \left( \frac{3}{6} - \frac{2}{6} \right) \] \[ = \frac{1}{7} + \frac{6}{7} \left( \frac{1}{6} \right) \] \[ = \frac{1}{7} + \frac{6}{42} \] \[ = \frac{1}{7} + \frac{1}{7} \] \[ = \frac{2}{7} \] 3) Ta có: \[ \left( \frac{-1}{3} + \frac{5}{6} \right) \cdot 11 - 7 \] \[ = \left( \frac{-2}{6} + \frac{5}{6} \right) \cdot 11 - 7 \] \[ = \left( \frac{3}{6} \right) \cdot 11 - 7 \] \[ = \left( \frac{1}{2} \right) \cdot 11 - 7 \] \[ = \frac{11}{2} - 7 \] \[ = \frac{11}{2} - \frac{14}{2} \] \[ = \frac{-3}{2} \] 4) Ta có: \[ \left( \frac{9}{10} - \frac{4}{5} \right) : \frac{2}{5} + 1 \] \[ = \left( \frac{9}{10} - \frac{8}{10} \right) : \frac{2}{5} + 1 \] \[ = \left( \frac{1}{10} \right) : \frac{2}{5} + 1 \] \[ = \left( \frac{1}{10} \right) \cdot \frac{5}{2} + 1 \] \[ = \frac{5}{20} + 1 \] \[ = \frac{1}{4} + 1 \] \[ = \frac{1}{4} + \frac{4}{4} \] \[ = \frac{5}{4} \] 5) Ta có: \[ \frac{3}{2} - \frac{1}{2} : \left( \frac{1}{4} - \frac{2}{3} \right) \] \[ = \frac{3}{2} - \frac{1}{2} : \left( \frac{3}{12} - \frac{8}{12} \right) \] \[ = \frac{3}{2} - \frac{1}{2} : \left( \frac{-5}{12} \right) \] \[ = \frac{3}{2} - \frac{1}{2} \cdot \left( \frac{-12}{5} \right) \] \[ = \frac{3}{2} - \frac{-12}{10} \] \[ = \frac{3}{2} + \frac{12}{10} \] \[ = \frac{3}{2} + \frac{6}{5} \] \[ = \frac{15}{10} + \frac{12}{10} \] \[ = \frac{27}{10} \] 6) Ta có: \[ \left( \frac{3}{4} + \frac{2}{3} \right) : \frac{17}{24} - \frac{3}{4} \] \[ = \left( \frac{9}{12} + \frac{8}{12} \right) : \frac{17}{24} - \frac{3}{4} \] \[ = \left( \frac{17}{12} \right) : \frac{17}{24} - \frac{3}{4} \] \[ = \left( \frac{17}{12} \right) \cdot \frac{24}{17} - \frac{3}{4} \] \[ = 2 - \frac{3}{4} \] \[ = \frac{8}{4} - \frac{3}{4} \] \[ = \frac{5}{4} \]